Posts Tagged ‘HDTV’

Classic Pete: Up On The Roof…Once Again

Three DTV antenna installations in two weeks — just another “day at the office?” Not for two of the homeowners involved, who are enjoying more free HDTV channels now.

It’s been a while since I got up on a roof with my tools and wired up an antenna system. With a whirlwind Panasonic dealer tour taking up most of my time in October (along with thousands of miles logged on United and US Airways), it was a nice break to put aside the computer and Powerpoint presentations, strap on my tool belt, and work with my hands.

As it turned out, I upgraded two systems and built a brand-new system for the third location. Off-the-shelf antennas and preamplifiers were used in each case, along with existing DTV sets and set-top boxes. Propagation tests and TVFool.com plots were used along with a Sencore SA1501 portable spectrum analyzer to align the antennas and verify reception at each location.

FIRST STOP: WALL TOWNSHIP, N.J.

I had previously set up this location a few years back to receive as many of the New York City DTV stations as I could. Back then, all of them were transmitting on UHF channels, but the combined antenna owned by CBS and mounted on the NW side of the Empire State Building still had pattern problems.

In particular, WNBC-28 was getting out horribly with a pattern that looked more like broken glass than a semi-circular shape. The pattern was so bad that I couldn’t even receive the station reliably when sitting on top of the Ramapo Mountains in NW New Jersey, looking directly at Empire with a Channel Master 4308 UHF yagi.

Following the analog shutdown on June 12, three NYC stations gave up their UHF assignments and moved back to highband VHF channels. WABC vacated channel 45 and returned to VHF-7, while WPIX turned UHF-33 over to WCBS and went back to VHF-11. WNET completed the trifecta by bailing out of UHF 61 (now out of the DTV core) and resuming transmissions on VHF-13.

Why didn’t WWOR move back to channel 9? Asleep at the switch, I’m afraid. WBPH in Allentown, who had been assigned UHF-60 originally, moved their operation to channel 9 and decided to stay put when the final channel elections were conducted. So, WWOR was forced to stay on UHF-38, carrying their own programs on minor channel #1 and duplicating WNYW’s telecast on minor channel #2. (The story behind that arrangement, along with WNYW simulcasting WWOR on 5-2, is best left for a future column.)


Figure 1. The “old” antenna setup (since June 2009) for VHF/UHF reception in Wall, NJ.

The original antenna setup (Figure 1) was a modified CM4308 driving a CM 7775 Titan 2 mast-mount preamp, fastened to a chimney atop a one-story house barricaded immediately to the north by tall trees. The location, just west of NJ Route 18, sits about 39 miles from Empire “as the photon flies” and was a good candidate for strong highband VHF reception, too.

The problem: The owner had originally replaced the CM4308 with a Channel Master 2016 and CM 7777 dual-band preamp at my suggestion to pull in 7, 11, and 13, but no luck. Channels 28 and 33 were solid, while WNYW-44 was in and out. Not good if you are a New York Giants fan and want to watch NFC games on Fox! Figure 2a shows the weak VHF signals on those channels using the original antenna setup, while figure 2b reveals that WNYW, while presenting with a clean waveform, has just barely enough carrier-to-noise to lock up reliably.

The fix: I ordered an Antennacraft Y5-7-13 five-element highband VHF yagi ($26.99 plus shipping) to replace the single angled half-wave dipole element on the CM2016, and set the internal combining switch on the CM 7777 preamp to separate VHF and UHF inputs. Out came the original CM4308 and it went atop a newer, taller mast (Figure 3).


Figure 2a. Highband VHF signals were weak through the CM2016.


Figure 2b. WNYW-44 was intermittent.

After careful aiming with the SA1501, it became apparent that, while the optimum heading for the VHF yagi was true to the TVFool prediction, the optimum heading for the CM4308 was about 5 degrees farther east to clean up the pattern from WNYW-44.

Figure 4a shows the improvements to channels 7, 11, and 13, adding NJ Public TV station WNJB-8 to the mix, while figure 4b shows UHF channels 25 through 40 all booming in. A stronger, dropout-free 8VSB waveform from WNYW-44 is seen in Figure 4c. (That’s WNJT-43 off the side of the antenna.)

Now, the homeowner has reliable reception of all major network channels, even in high winds (which we experienced that day) using a DirecTV set-top receiver with ATSC tuner. That means was able to see the NY Giants get their butts kicked on successive weekends by the Cardinals and Eagles! (Be careful what you wish for…)

Note that, as of this writing, Channel Master has discontinued the CM4308 from its catalog. Not to worry! You can use a CM2016 in its place — just don’t connect the single dipole VHF element, although you should fold it out into its normal position.


Figure 3. The new split-stack UHF/VHF array, showing the offset for UHF reception.


Figure 4a-b-c. Now, channels 7 through 13 are solid (left), while UHF stations are slightly stronger (center) and WNYW-44 has lots more headroom (right).

SECOND STOP: HOME SWEET HOME

Not many people come home from church services at noontime on a sunny, warm day and say, “Gee, I think I’ll go up on the roof and change out my antenna system!” But I’m a bit strange that way. My wife asked me if she should stick around to help out while I was up there, but I assured her I was perfectly capable of falling off a roof by myself with no additional help. (Black humor…)

Turns out, I ordered two of the Antennacraft Y5-7-13s, which (for some strange reason) they insist on shipping FedEx Green with signature required. Apparently, theft of TV antennas from front porches is a problem in some parts of the country?

Last December, I had replaced my old setup with a pair of CM 2016s, stacked and offset on a rotatable mast. The offset was designed so that when the bottom antenna was aimed towards Philadelphia, the top antenna was aimed towards New York City (60+ miles away, over two ranges of hills).

The problem: As things turned out, I rarely need to move the Philly antenna, but I did rotate the top CM2016 frequently to pick up stations as far away as Scranton/Wilkes-Barre (70+ miles, also over two ridges). Alas, after 6/12/09, I lost WABC, WPIX, and WNET completely as they moved back to the VHF band. As I discovered at the previous location, the CM2016s weren’t up to the job of pulling in these stations, even though they did snag WBRE-11 and WYOU-13 from Scranton — pretty impressive for a single half-wave dipole!

Figure 5. My lower, fixed CM2016, aimed permanently towards the Roxborough (Philadelphia) antenna farm.

Figure 6. The new UHF/VHF stack, aimed towards New York. Told you it was a beautiful day for antenna work!

The fix: This was a three-art solution. First, I removed the lower CM2016 and fastened it to the rotor support, permanently aimed SSW towards Roxborough, about 22 miles away as seen in figure 5. It feeds the combined input of a CM 7777 preamp, necessary because I split the signal several times to distribute it through the house.

Next, I re-installed another CM4308 atop the mast and Y5-7-13 below it, both feeding another CM 7777 preamp in split-input mode. This array would become my “DX” antenna (figure 6), although I anticipated leaving it aimed towards New York most of the time.

Results were encouraging, although not perfect. Figure 7a shows the RF spectrum from channels 7 through 13 before the upgrade, while figure 7b shows the same channels afterwards. Not a substantial difference to be sure, except that the antenna is now more selective and I gained some C/N headroom on channel 7. WPIX-11 and WNET-13 are largely unchanged, which would imply that I had some enhanced propagation when I took the original measurements back in late June of 2009.

Reception of all three VHF channels continues to be problematic, although each has gotten much stronger. Channels 11 and 13 in Scranton are no doubt causing co-channel interference problems, so I may never get that resolved. As for WABC-7, I don’t think the station is running enough power for highband VHF operation — another 3 or even 6 dB would seem to be in order.

Figures 7a-b. Channels 7 through 13 as received on the old CM2016 (left) and the new Y5-7-13 (right).

Figure 8. There’s lots of RF coming in from New York on the low UHF band!

On UHF, signals just barrel in, as seen in figure 8. WNBC-28, WCBS-33, WWOR-38, and WXTV-40 are all strong, 24/7. Unfortunately, WNYW-44 can’t get through because of co-channel interference from WMCN-44 in south Jersey (no NY Giants NFC games…sigh…), while WPXN-31 just isn’t strong enough to peek through.

Supposedly, an upgrade to the combined VHF antenna atop Empire is in the works for 2010, according to sources in the industry. Maybe that will change things for the better!

LAST STOP: SAUGERTIES, N.Y.

My last trip was up to the foothills of the Catskills on a rainy, foggy early morning. My goal? Install VHF and UHF antennas for reception of Albany and Schenectady DTV stations, allowing the homeowner (my youngest brother) to “cut the cord” and drop expensive cable TV channel packages while retaining broadband service from Time Warner.

The problem: This location, on the side of a hill and about 35 miles from the Helderberg Mountain antenna farms over a 1-edge path, didn’t look to be particularly difficult. (Figure 9) I had run some UHF DTV reception tests at this location a few years back with encouraging results. At the time, most of the Albany DTV stations were on UHF, with a couple plugging away on highband VHF. Post-transition, I’d need to pull in WRGB-6, WXXA-7, WNYT-12, WNYA-13, WTEN-26, WMHT-34, and WCWN-43 at the least.

Figure 9. The Saugerties location had a nice, nearly flat roof to work on.

Figure 10. Here’s the final UHF/VHF stack with the CS600 on the bottom.

The fix: Because the Albany market has a lowband VHF DTV operation (WRGB-6), I ordered Antennacraft’s CS600 dual-band yagi ($34.72 + shipping), the same antenna that is currently sitting about a foot off the ground at the “fringe” SW Vermont location I wrote about this past August.

UHF reception would be taken care of by yet another CM 4308, sitting a few feet above the CS600 on the stack. (Figure 10) A quick test with my spectrum analyzer showed that it didn’t much matter where I mounted the antenna on the roof — I’d have plenty of signal to work with, except from WNYA-13. This channel exhibited low signal levels no matter where I spotted the mast.

(Subsequent email chats with one Albany DTV engineer revealed that the WNYA-13 DTV antenna system does not get out as well as other stations and is side-mounted on the old WRGB analog channel 6 tower — PP)

Each antenna drove the separate inputs of a CM 7777 mast-mounted preamp (gotta love it!), which in turn was scheduled to go into an existing eight-way splitter from the original cable TV distribution system. As it turned out, only four of the taps on the splitter actually led to any TVs or wall-mounted jacks, so I swapped it out for a more reasonable four-way split arrangement.

Figure 11a-b-c. WRGB-6 is super strong (left), while WXXA-7 (center) and WNYT-12 and WNYA-13 (right) are sufficiently powered up.

Figures 12a-b-c. WTEN-26 (left) is another monster signal out of Albany, while WMHT-34 (center) and WCWN-43 (right) are “merely” strong enough!

Figure 11a shows the unbelievably strong signal from WRGB-6, boosted shortly after 6/12 to overcome possible interference from those adjacent FM broadcast stations and also to fill in holes in signal coverage. Figure 11b shows WXXA-7; while figure 11c lets you clearly see the power disadvantage of WNYA-13 (right) compared to WNYT-12 (left).

As for UHF, you can see the strong signal from WTEN-26 in figure 12a (that’s WTBY-27 to its right, many miles SE of my location), with WMHT-34 and WCWN-43 visible in figures 12b and 12c, respectively. WYPX (ION) from Amsterdam just wasn’t strong enough to lock up on either of the Digital Stream DTV converter boxes I installed in the house — too far away.

Oddly enough, WNYA-13 will only come through on two of the three active RF feeds in the house, even though a test of signal levels showed all three to be about the same. Switching converter boxes out didn’t make any difference, so there may be a problem in one of the coaxial lines I’ll have to ring out on a future visit. In the meantime, the system was up and running in time for us to watch Game 3 of the World Series…even if it was downconverted digital TV of an old Philips CRT set.

Tech notes: Antennacraft yagis are designed with square booms and cannot use conventional round boom hardware that is common to Channel Master yagis. You will get a hardware bag with the antenna — don’t lose it! Also, you will need to purchase a balun transformer separately to make your coaxial feed, as Antennacraft doesn’t provide baluns or weatherproof boots with their yagis.

Figure 13. Here’s one way to attach a round balun to a square boom. (Sounds like one of those mental puzzles from my childhood…)

Figure 13 shows a Channel Master balun attached to a Y5-7-13 and secured with tape. It’s a good idea to form the balanced wire connections into drip loops and mount the balun underneath the antenna. Also, add a drip loop to the coax feed before it attaches to and travels down the mast.

Classic Pete: Once More, Out To The DTV Fringe

Recently, I made a third trip to my brother’s house in the hills of southwestern Vermont to finish what I started over two years ago – set up this distant, remote location to receive every digital TV channel from Albany. And I succeeded.

 

 

My first visit in May of 2007, chronicled here, showed that a modest suburban UHF yagi (Channel Master’s model 4308) and a low-noise preamp was sufficient to pull in four Albany DTV stations over a 54-mile path by taking advantage of knife-edge refraction of the RF signals, bending over a range of hills about ½ mile to the southwest of the house.

I was surprised at how strong the “bent” signals were, even with moderate multipath distortion. But they came in just fine on a pair of Gen5 ATSC DTV receivers, with minor interruptions in service during periods of heavy rain or dense fog.

Still, I hadn’t resolved the issue of receiving a pair of high-band Albany VHF DTV channels – WXXA-7 (Fox) and WNYT-12 (NBC). That would be addressed during my next visit in early January of this year, and you can read about it here. Trust me; it wasn’t much fun working outside in sub-zero temperatures. And I didn’t have the best antenna for the job, relying on a used Terk TV35 suburban VHF/UHF yagi to pull in the signals, aided by a dual-band, low noise preamplifier.

I knew a third and final tweak to the system would inevitably be in order, particularly to improve the reception of WXXA-DT. Plus, WRGB-DT (CBS), previously operating on UHF channel 39, was scheduled to move back to VHF channel 6 on June 12 as the analog TV shutdown was completed. And another Albany DTV station, WNYA (MyTV), hadn’t even signed on yet- they were still waiting for WNYT to vacate their analog signal from channel 13.

 

 

THE FINAL PUZZLE PIECE

The first order of business was to replace the Terk TV35 with a more serious VHF yagi. Fred Lass, chief engineer at WRGB, kindly sent along a pair of Antennacraft Y5-2-6 low-band VHF yagis for the job, but those wouldn’t help me with channels 7, 12, and 13.

Instead, I opted for the Antennacraft CS600 VHF yagi, which would provide reception from channel 2 through 13 and which (according to the specs) was good for up to 40 miles on low-band VHF and 50 miles on high-band VHF. Coupled to the Channel Master #7777 dual-band preamp, I figured it would be enough.

The next step was to check reception from the January installation by recording new spectrum analyzer plots and comparing them to the screen grabs I captured eight months ago. Good news – the 8VSB carriers from the remaining UHF stations (WTEN-26, WMHT-34, and WCWN-43) hadn’t changed any, even with all the nearby trees fully leafed out.

Unfortunately, signals from WXXA-7 and WNYT-12 didn’t look too good, thanks to a broken rear reflector element on the TV35. So, I removed the Terk from the system and assembled the CS600. I also had to install a second, offset antenna mast to clear the rear elements of the CS600 from the deck supports, not to mention a large rose bush which had grown around the mast and TV35!

 

 

 

 

 

To make everything fit in this tight space, I drilled a set of new boom-to-mast bracket holes near the rear of the CS600. The antenna is light and sturdy enough to be mounted this way, although I recommend using the standard mounting holes when up on a rooftop mast to balance the antenna and reduce wind load.

From my January escapades, I found that the TV35 worked better when it was offset about 30 degrees farther west from the UHF antenna heading. I chalked that up to different reflections of the knife-edge signal than I had seen on UHF, and initially installed the CS600 at the same height, facing in the same direction.

A quick test with a Zenith DTT901 NTIA converter grabbed WRGB-6, WNYT-12, and newcomer WNYA-13 with no difficulty. But WXXA-7 was intermittent, and now WMHT-34 (PBS) was becoming problematic to receive. This wasn’t going to be easy! (It never is…)

ZEROING IN

In my January conversations with Fred Lass, he mentioned that the refraction angle for channel 6 could be more severe than that of the UHF DTV stations. That meant I might have more luck if I lowered the CS600…and that’s exactly what happened.

After a night to clear my head and socialize with my relatives, I walked outside early the next morning, connected my spectrum analyzer, loosened the mast bracket, and lowered the CS600 to within a foot of the ground. I also rotated it south to the same antenna heading (230 degrees) that I eventually used to clean up reception of WMHT-34 on the Channel Master 4308.

 

After firing up the DTT901, I was finally done. All eight of the Albany DTV stations were now coming in reliably, free of dropouts. WXXA-7’s waveform, although still somewhat bowed, was considerably cleaner than before. And a modest amount of tilt on WNYT-12 and WNYA-13 was no problem even for the adaptive equalizers in my Gen 5 OnAir Solution HDTV-GT receiver.

In fact, I had enough signal out of the CM 7777 preamp to run a second coaxial drop upstairs to a bedroom, feeding a second DT901 converter box with the same results. Oddly, WRGB’s signal on channel 6 remained consistent through the CS600 at any height and with either of the compass headings I used. The 8VSB carrier wasn’t perfectly level, but the converter boxes and HDTV-GT locked it up quickly every time.

 

PROBLEM SOLVED

When TV signals bend, they really bend! Knife-edge refraction works so well at this location that I actually received all of the Albany DTV channels with the CS600 resting nose-down on the ground and its rear elements tilted up at a 45-degree angle against the mast! That certainly was cool.

The only weather effects I observed happened the last night of my stay, when dense clouds of moisture formed in the valley right before a strong weather front passed through. The resulting mist and fog caused ABC affiliate WTEN-DT’s signal on channel 26 to break up on a regular basis, while all other channels were unaffected. The next morning, all was well again. (Coincidentally, I’ve observed the same effect at home on Philadelphia’s KYW-DT, also transmitting on channel 26 and otherwise a very strong and reliable signal.)

Because the CS600 sits so low on the mast, I wrapped the longest elements with bright orange electrical tape so no one would walk into it. I also capped the swaged ends of the elements with plastic bolt protectors, glued in with silicone seal. Some new flower plantings around the antenna should keep visitors from accidentally walking into it in the future. (Don’t these problems sound ridiculous?)

 

 

Now, my brother and sister-in-law are going to try terrestrial digital TV for a month and see if they still want to pay for their existing DirecTV service. Given how little television my brother watches, I think I know how he’ll cast his vote, but I’m not sure about his wife.

I will say that she showed remarkable enthusiasm for finally having gained access to “free TV,” and she subsequently informed me that there would be a stampede for my services from nearby neighbors who’d also want in on this deal. Maybe it’s a good thing that I live almost 300 miles away?

I’m also amazed at how robust the 8VSB DTV system turned out to be, and how it’s perfectly suited to unusual propagation paths like this one. Granted, I also pulled in analog VHF and UHF TV stations with the earlier antenna setups, but the signals were fairly noisy and had more than a few ghosts, as you might expect.

Digital TV cleans all of that up. All you need is enough signal to get over the required carrier-to-noise threshold (in this case, about 20 dB C/N), and voila – perfect pictures and audio. (Never mind that a few of them were infomercials.) The fact that converter boxes and new integrated digital TV sets are largely using Generation 6 adaptive equalizers is just icing on the cake.

 


Any disappointments? Well, I never could pull in WYPX-50 from Amsterdam, although it’s strong enough to show up on my spectrum analyzer. The problem is their transmitter location, much farther west than the Helderberg Mountain antenna farm used by everyone else. That would require “sacrificing the good of the many for the good of the one” (to misquote Mr. Spock from Star Trek II: The Wrath of Khan).

Also, I could see another 8VSB carrier on channel 9 from WVER (Vermont Public Television) in Rutland, Vermont. But to receive that station would have required divine intervention, as the signal was coming from the opposite direction, 34 miles to the north/northeast over a tall range of hills, including Mt. Equinox (3,848’ ASL), and ricocheting off the 1300-foot-tall ridge in front of the house. Now, THAT would have been one heck of a billiards shot!

The good news is, if you live in a “tough” DTV reception location, you may not be completely out of luck. It helps if the DTV stations you want to receive are co-located, because having only one antenna heading to deal with is a real blessing. But there’s no reason why you couldn’t succeed with a broader antenna pattern if DTV stations are spread farther part – you just need to get enough signal to the receiver, and you’re home free.

As they used to say in those old Westerns, “Looks like my work here is done.” Time to saddle up, and head off in search of the next fringe…